During the 2012 Republican primary, Rep. Michele Bachmann committed many errors, but her worst offense was probably going on TV to lodge an unsubstantiated attack against Texas Gov. Rick Perry.

As you might recall, Perry had once supported mandating teenage girls in Texas be vaccinated against HPV. “There’s a woman who came up crying to me tonight after the debate,” Bachmann said on air. “She said her daughter was given that vaccine. She told me her daughter suffered mental retardation as a result of that vaccine.”

The most charitable analysis that can be offered in this case for Bachmann is that she got duped into repeating a vaccine-scare urban legend on national television. It looks more like Bachmann sensed that she had won a point and wanted to go in for the kill, didn’t bother to check the facts, and didn’t care that she was stoking an anti-vaccination paranoid conspiracy theory, either. Neither shines a particularly favorable light on Bachmann.

This was amateur hour, and you might say, that’s just Bachmann being Bachmann. No respectable politician would make such an unsubstantiated charge in public — not without having the goods — right? Wrong.

Enter Majority Leader Harry Reid, who decided it would be appropriate to pass along an anonymous allegation he supposedly heard (although, who knows?) — that Mitt Romney had not paid taxes for a decade.

This unsubstantiated allegation was generally mocked, even by the establishment press.